Springs for seats and backs



March 12, 1963 Filed Iarch'7, 1961 R. D- STROUT ETAL SPRINGS FOR SEATS AND BAcKs 2 Sheets-Sheet 1 INVENTORS RAYMOND D. ST ROUT YLYNN W. STAPLES I awg w hr ATTORNEYS March 12, 1963 R. D. STROUT ETAL SPRINGS FOR SEATS AND BACKS Filed March 7, 1961 2 Sheets-Sheet 2 IN VEN TORS RAYMOND D. STROUT BY LYNN W. STAPLES ,zv% ATTQRNEYS United States Patent 3,081,076 SPRINGS FOR SEATS AND BACKS Raymond D. Strout and Lynn W. Staples, Saginaw,

Micln, assignors to Saginaw Wire Products, Inc., Saginaw, Micln, a corporation of Michigan Filed Mar. 7, 1961, Ser. No. 93,914 14 Claims. (Cl. 267-107) This invention relates to springs of the type employed in vehicle seats and to certain novel and useful improvements therein. The application is a continuationin-part of application Serial No. 821,412 filed June 19, 1959, now Patent No. 3,024,016.

' Presently, springs having sinuous wire deck sections are designed to assume a certain predetermined contour under load which is comfortable to the occupant. springs of this character which have predetermined defiection characteristics under the weight of an occupant are disclosed in Patent No. 2,829,880.

One of the prime objects of the present invention is to provide a spring, with predetermined deflection characteristics, which can be used in a seat having its rear support rail disposed above the front support rail so that the space immediately beneath the rear rail is available for toe room. A spring of the type which has been used where similar space limitations exist is disclosed in Neeley Patent No. 2,830,654, but springs of this design do not provide the comfort which applicants assignee desires.

It is a primary object of the present invention to design a spring strip which includes a rear support arm configured to effectively support the forces which are applied to the maximum load receiving portions of the deck while at the same time enhancing the sinking or settling of the rear edge of the deck which has so much bearing on seat comfort.

A further object of the invention is to design a spring of the character described in which the configuration of the rear support arm is related to the cross-sectional configuration of the deck section of the spring and is, in fact, in one embodiment of the invention carried over to the rear loop thereof to provide the desired rigidity in this area of the spring.

A further object of the invention is to provide a spring strip which is of such design that minor changes can be made at localized points to permit variance of the contour assumed under load to suit the different requirements of different manufacturers.

Still a further object of the invention is to design a practical spring strip, particularly suited to certain seats wherein provision must be made for passenger toe room and available deflection space is severely restricted, which can be economically produced on a mass production basis to provide a spring of reliable construction which uses a minim=alamount of wire.

With the above and other objects in view, the present invention consists in the combination and arrangement of parts hereinafter more fully described, illustrated in the accompanying drawings, and more particularly pointed out in the appended claims, it being understood that equivalent changes may be made in the various elements which comprise the invention without departing from the spirit thereof or the scope of the appended claims.

In the drawings, FIGURE 1 is a side elevational view disclosing a vehicle seat spring assembly formed in accordance with the present invention;

- FIGURE 2 is a top plan view thereof; FIGURE 3 is an enlarged, transverse view taken on the line 33 of FIGURE 2;

FIGURE 4 is a schematic, side elevational view illustrating typical deflected positions of old type springs and the present spring;

Formed.

, front seat frame.

Patented Mar. 12, was

FIGURE 5 is a side elevational view of a modified spring;

FIGURE 6 is a top plan view thereof; and

FIGURE 7 is an enlarged, sectional view taken on the line 77 of FIGURE 5.

Referring now more particularly to the accompanying drawings, a letter S generally indicates a resilient wire spring strip, constructed in accordance with the invention, which is shown secured between the front and rear rails 10 and 11, respectively, of a conventional, automotive, It Will be observed that the rear rail 11 is located a substantial distance above the front rail 10 to provide for toe room under and forwardly of the rear rail 11. There will, of course, be a plurality of such spring strips connected between the'front and rear rails of the front seat frame at transversely spaced intervals and joined by a border wire to form a spring cushion, as in Flint Patent No. 2,684,844, for instance, and the springs will be covered with fabric 12 and padding 13, as usual.

Each spring S has a deck section of sinuous, generally rectangular loop form, identified generally by the letter I), which includes a front end support section generally designated F and a rear arm support section generally designated R. The front end support section F comprises a pair of generallyS-shaped, divergent leg portions 14- and 15 joined by a torsion section 16 and is connected by i a torsion bar 17 to the deck section D. Provided on the front frame member 10 is a clip 18 which accommodates the lowermost torsion section 19 of the front section F and this section 19 has an angularly bent stub portion 19a, as shown, which permits section 19 to torsionally resist a load applied to the spring.

The deck section D is provided with oppositely facing, generally rectangular loops having spacer bars 20 of substantially uniform length and torsion bars 21 of varied length, dependent on the contour which the deck section is to assume under load. The maximum load of the seat occupantis applied to the deck section of the spring at the point A Where the buttocks of the seat occupant bears upon the spring at a point approximately two thirds of the length of the deck section from the front end thereof.

The rear arm section R is sinuous in configuration, as shown clearly in FIGURE 2, with loops that open transversely of the axis of the spring, as do the loops of the deck section D, but are much narrower in width and have torsion bars 22 of considerably greater length than the spacer bars 2.3 which can be curvilinear. From the point 5 to the point 0 the annular wire is of rectangular cross-section and is of greatly decreased Width and greatly increased depth relative to the cross-section of the remainder of the spring, which is circular. This crosssection of rectangular configuration occurs, as noted, in the major portion of the rear arm section R, in the major portion of the rear loop (I of the deck section D, and in the loop portion 2 which connects the deck section D and rear arm section R.

Provided on the rear frame member 11 is a clip 24 which accommodates the uppermost torsion section 25 of arm section R and itwill be seen that torsion bar 25 has an angularly bent stub end 25a which similarly permits it to torsionally resist loads applied to the spring S. When mounted in position as shown in FIGURE 1, the spring S is, in fact, pre-loaded to resist deflection. In this connection, the unloaded position of stub end 10a is generally parallel with the lowermost spacer bar 26 of the front end section F.

The spring will assume the contour indicated by the broken lines f in FIGURE 4. Generally speaking, most of the weight of the hips will be transferred to the area of the spring near point A, as noted.- This is the point about the neutral axis. The relationship is expressed by the following formula:

(the letter M designating the bending moment at that point as a result of the imposed load).

The moment of inertia in bending for the section of Wire can be expressed by the following formula:

(where h is the depth or vertical dimension of the wire section and b is its horizontal dimension or width).

Thus, it will be seen that deflection is a function principally of the depth of the wire section at a particular point ecause the depth ([1) has a third power effect on deflection. The greatly increased depth of the rear loop section (1 provides a deck portion of increased rigidity and resistance to deflection at the rear end of the deck section which must bear the maximum load imposition. Also, with the depth of the major portion of the rear arm section R being substantially increased, it has been determined that resistance to torsion is greatly increased and there is greater resistance to movement of the lower end of the rear arm section R or loop portion e forwardly and to consequent flattening of the rear arm section R. In considering the matter of torsional resistance it is helpful to note that the angle of twist through which any torsion bar 22 is deflected is inversely proportional to the polar moment of inertia in torsion about its vertical axis. it has been determined that the polar moment of inertia of a wire of rectangular cross-section in which the depth is three times the width is 1.75 times the polar moment of inertia of a wire of the same cross-sectional area which is circular in cross-section and the angle of twist under a given load is reduced 1.75 times. This factor in the spring of the present invention tends to provide more support at the A point and hold the A point of the spring up.

Because the width of the torsion bars and spacer bars 23 is greatly reduced, the arm section R elongates far more readily and the result of its decreased resistance to elongation and increased torsional resistance is to provide a more nearly vertical settling of the buttocks in the seat, which tends to avoid the chafing action noticeable during long trips with seats having springs of diflerent design. Thus, the design tends to retain the crown of the deck section D while providing the desirable drop in effect. Differently stated, the design tends to hold the A point up while allowing the portion rearwardly thereof to drop more readily. The eifect, when a load is applied, is illustrated in FlGURE 4, wherein solid line "3 indicates a spring of either the prior art type mentioned or the present design prior to application of the occupants weight and diagrammatic line It represents the deflected position of a spring of the prior type. As previously noted, broken line f is illustrative of the deflected position of a spring of the present design. The letter 1- represents the position of the rear end of the deck section prior to deflection, the letter r represents the deflected position of the rear end of the deck section of the prior art spring of this type, and the letter r represents the deflected position of the rear end of the deck section of a spring of the present design under the same load. It will be observed that the A point deflection is substantially the same, while the 1' point deflection with the spring of present design is substantially greater.

The spring is formed in the manner indicated in our co-pending application referred to supra, with wire stock of annular cross-section in predetermined length, being fed through rolls or dies of the type shown, the rolls or dies being configured to flatten the annular wire between the sections b and c. The wire is then processed to a wire bending machine wherein it is sinuously formed, and finally to another bending machine for bending the front and rear sections F and R out of the plane of the deck portion D.

In a modified. embodiment of the invention the deck section D is formed in the manner shown in FIGURES 1-5 of our co-pending application Serial No. 821, 12 with the rear arm section R of the present invention, including loop 2, replacing the rear end torsion bar 23 of the rear support section R. This design is particularly useful for seats in which the rear support rail is raised substantially above the front support rail.

Another embodiment is shown in FIGURES 5-7, wherein the spring S is shown as having a deck section generally designated D which includes a front end support section generallydesignated F and a rear arm support section generally designated R. The front end support section F comprises a pair of divergent leg portions 14' and 15' joined by a torsion section 16, and is connected by torsion bar 17' to the deck section D. Clip 18' similarly accommodates the lowermost torsion section 19 of front section F and an angularly bent stub portion 19a is provided. It will be seen that the spacer leg portions 14 and 15' are fiatted and present sections of increased width and decreased depth relative to the other portions of deck section D and front support section F.

Section D'- similarly has spacer bars 2!) and torsion bars 21, and rear arm section R includes spacer bars 23' and torsion bars 22'. The rear arm section R, instead of being joined to the rear edge of the deck section D, however, includes what is termed a fishtail section comprising divergent spacer bars 29 and 33 connected by a torsion bar 31. The upper spacer bar 29 is joined to the rear of deck section D by torsion bar 32. Provided on the rear frame member 11' is a clip 24' which accommodates the uppermost torsion section 25' of arm section R and a similar stub end 25a forms the terminal end of the spring S, as previously.

The rear arm portion R is flatted in the opposite direction from portions 28 from a point 32 to a point 33. The incorporation of the fishtail section, including the spacer bars 29 and 30 and torsion bar 31, tends to drop the r point even further and provides optimum comfort. The spacer bar 30, in view of its increased depth over the section of circular cross-section, is considerably more resistant to deflection as a beam, and the result is to tend 'to hold the A point up more than would be the case were the spacer bar 30 of circular cross-section.

With spacer bars 14' and 15 flatted as at 28, the front portion F of the spring has greater flexibility and for a wire of given elastic limit can provide a much softer front end action, it being assumed that torsion bar 16 will be stressed within the elastic limit of the wire. The spring of FIGURES 5-7 provides optimum comfort while still allowing passenger toe room under the rear support section R.

It should be apparent that we have perfected a greatly improved spring strip well suited to the particular application for which it is intended, which can be practically produced in present wire spring forming plants with present equipment.

It is to be understood that the drawings and'descriptive matter are in all cases to be interpreted as merely illustrative of the principles of the invention rather than as limiting the same in any way.

We claim:

1. A spring comprising a resilient wire spring with a load supporting deck section having a front end support section adapted to be attached to a front rail; said deck section also having an upwardly extending rear support arm, including a sinuous portion, adapted to be connected to a rear support rail; the said deck section and arm being formed of a single wire of uniform cross-sectional area with the said sinuous portion including a flat portion of decreased width and increased depth relative to the width and depth of a substantial portion of the deck section.

2. A spring comprising a resilient wire spring with a load supporting deck section having a front end support section adapted to be attached to a front rail; said spring also having an upwardly extending rear support arm, including a sinuous portion, supporting the rear end of said deck section and adapted to be connected to a rear support rail; the said deck section and arm being formed of a single wire of uniform cross-sectional area with the arm including a flat portion of decreased width and increased depth relative to the width and depth of a sub-' stantial portion of the deck section.

3. A spring strip comprising a resilient wire spring with a load supporting deck section having a front end support section adapted to be attached to a front rail; said deck section also having an upwardly extending rear support arm; the said arm including a pair of spacer portions joined by a torsion portion and the arm and deck section being formed from a single wire of circular crosssectional area with the arm including a flatted portion of different width and depth than circular portions of the wire.

4. A spring comprising; a resilient wire spring including a load supporting, sinuous deck section with a fishmouth front end support section at its front end for mounting said spring on a front rail; and an upwardly and rearwardly extending rear support arm, having a portion of sinuous configuration constituting the major portion of the arm, joined with the rear end of said deck section and mounting said spring on a rear rail, the said spring being formed of a single wire of uniform cross-sectional area, circular except for the rear portion of said deck section and the major portion of said rear arm section; said rear portion of the deck section and major portion of said rear arm section being of decreased width and increased depth relative to the remainder of said spring.

5. A spring structure comprising; a front support rail; a resilient wire spring including a load supporting, sinuous deck section with a fishmouth front end support section mounting said spring on said front rail; a rear support rail above said deck section; and an upwardly and rearwardly extending rear support arm having a portion of sinuous configuration constituting the major portion of the arm joined with said deck section and mounting said spring on the rear rail, the said spring being formed of a singlewire of uniform cross-sectional area, circular except for the rear portion of said deck section and the major portion of said rear arm section; said rear portion of the deck section and major portion of said rear arm section being of decreased Width and increased depth relative to the remainder of said spring.

6. The combination defined in claim 1 in which said deck section has oppositely facing, generally rectangular loops with torsion bars of varied length shorter than spacer bars which connect them.

7. The combination defined in claim 1 in which said deck section is linear.

8. The combination defined in claim 1 in which said deck section is substantially linear and includes a tapering section decreasing gradually in depth while increasing correspondingly in width intermediate the ends of the deck section.

9. The combination defined in claim 2 in which said rear support arm includes a pair of divergent spacer portions connected by a torsion section and joining said sinuous portion to the rear edge of the deck section; the lowermost spacer portion comprising a flat portion of decreased width and increased depth relative to the width and depth of a substantial portion of the deck section.

10. The combination defined in claim 2 in which said front end support section includes a pair of divergent spacer portions connected by a torsion portion with at least one of the spacer portions having a portion of increased width and decreased depth relative to the like dimensions of the torsion portion.

11. A spring structure comprising a resilient wire spring with a load supporting deck section having a front end support section adapted to be attached to a front rail and a rear end support section adapted to be attached to a rear rail; said deck section and a support section being formed of a single wire of uniform cross-sectional area with the said support section including a pair of divergent spacer portions below the deck section joined by a torsion portion; at least one of the spacer portions having a por tion of different width and depth relative to the like dimensions of the torsion portion.

12. A spring structure comprising a resilient wire spring with a load supporting deck section having a front end support section adapted to be attached to a front rail and a rear end support section adapted to be attached to a rear rail; said deck section and at least one end support section being formed from a single wire of uniform circular cross-sectional area with the said one end support section including a pair of spacer portions joined by a torsion portion; at least one of the spacer portions having a fiatted portion of different width and depth than the circular portions of the wire.

13. A spring comprising a resilient wire spring with a load supporting deck section having a front end support section adapted to be attached to a front rail; said deck section also having an upwardly extending rear support arm, including a sinuous portion, adapted to be connected to a rear support rail; the said deck section and arm being formed of a single wire of uniform cross-sectional area with the said sinuous portion including a flat portion of different width and depth than the width and depth of a substantial portion of the deck section.

14. A spring comprising a resilient wire spring with a load supporting deck section having a front end support section adapted to be attached to a front rail; said spring also having an upwardly extending rear support arm joined to said deck section by a torsion portion and supporting the rear end of said deck section, adapted to be connected to a rear support rail; the said deck section and arm being formed from a single wire of circular cross-sectional area with the arm including a flatted portion of diiferent width and depth than circular portions of the wire.

References Cited in the file of this patent UNITED STATES PATENTS 2,639,763 Neely May 26, 1953 2,910,115 Meyers Oct. 27, 1959 2,925,855 Caughey Feb. 23, 1960 

1. A SPRING COMPRISING A RESILIENT WIRE SPRING WITH A LOAD SUPPORTING DECK SECTION HAVING A FRONT END SUPPORT SECTION ADAPTED TO BE ATTACHED TO A FRONT RAIL; SAID DECK SECTION ALSO HAVING AN UPWARDLY EXTENDING REAR SUPPORT ARM, INCLUDING A SINUOUS PORTION, ADAPTED TO BE CONNECTED TO A REAR SUPPORT RAIL; THE SAID DECK SECTION AND ARM BEING FORMED OF A SINGLE WIRE OF UNIFORM CROSS-SECTIONAL AREA WITH THE SAID SINUOUS PORTION INCLUDING A FLAT PORTION OF DECREASED WIDTH AND INCREASED DEPTH RELATIVE TO THE WIDTH AND DEPTH OF A SUBSTANTIAL PORTION OF THE DECK SECTION. 